[DOC] Document `cluster.search.ignore_awareness_attributes` setting

[bowenlan-amzn]

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Tell us about your request. Provide a summary of the request.

I have a AWS customer asking why preference= doesn't route to same shard. Their cluster has 3 availability zones.
Turns out in AWS cluster.search.ignore_awareness_attributes is default to false, but open source is default to true.
We should document this setting in this page probably
https://docs.opensearch.org/docs/latest/search-plugins/searching-data/search-shard-routing/

Regarding AWS behavior, please suggest where to document if you know

Version: List the OpenSearch version to which this issue applies, e.g. 2.14, 2.12--2.14, or all.
all
introduced here opensearch-project/OpenSearch#1107

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.

[kolchfa-aws]

@bowenlan-amzn Is this on track for 3.1?

[kolchfa-aws]

This is not specific to 3.1 so removing the 3.1 label

[natebower]

@bowenlan-amzn Would you be willing to create a PR addressing your issue?